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Fencer Vulns
critical 9.8

CVE-2026-74727 in the critical feed json

ovpn: skip rehash for peers already removed from by_id

published 2026-08-22 2 mo ago modified 2026-10-14 26 d ago also EUVD-2026-64414

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

ovpn: skip rehash for peers already removed from by_id

ovpn_nl_peer_set_doit() resolves the target peer via ovpn_peer_get_by_id() before taking ovpn->lock. In the window between the lookup (which only takes a refcount) and the subsequent spin_lock_bh(&ovpn->lock), a concurrent OVPN_CMD_PEER_DEL, keepalive expiry, or socket teardown can take ovpn->lock first, run ovpn_peer_remove() to unhash the peer from all four tables (by_id, by_vpn_addr4/6, by_transp_addr) and release the lock. set_doit then acquires ovpn->lock and calls ovpn_peer_hash_vpn_ip(), which re-inserts the now-removed peer back into the rehashing tables.

The same race affects the float path: ovpn_peer_endpoints_update() holds only a refcount and acquires ovpn->lock very late (after async AEAD decrypt and a netlink notification), then rehashes the peer in the by_transp_addr table.

The resurrected peer becomes reachable again from the RX lookup (ovpn_peer_get_by_transp_addr) and the TX VPN-IP lookup, even though userspace believes it is gone. Once the data-path refcount drops the peer is freed via call_rcu while the hash entries embedded in it remain linked, opening a UAF window.

Bail out of the rehash when hash_entry_id is unhashed, mirroring the sentinel already used by ovpn_peer_remove() to detect the already-removed state. The check is safe under ovpn->lock, which serializes every mutation of hash_entry_id, and is a no-op for the add path because ovpn_peer_add_mp() inserts hash_entry_id before calling ovpn_peer_hash_vpn_ip().

Patch / fix

  • Linux Linux 6.18.45, 7.1.9, 7.2
  • linux Debian 14 7.1.9-1

debian advisories DEBIAN-CVE-2026-74727

  • linux Ubuntu 26.04 LTS 7.0.0-42.42
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1017.17
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-42.42.1
  • linux-oracle Ubuntu 26.04 LTS 7.0.0-1015.16
  • linux-hwe-7.0 Ubuntu 24.04 LTS 7.0.0-42.42~24.04.1
  • linux-oem-7.0 Ubuntu 26.04 LTS 7.0.0-1017.17

ubuntu advisories UBUNTU-CVE-2026-74727

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-74727 updated cvss 5.5

kernel: ovpn: skip rehash for peers already removed from by_id

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.